PHP Internals News: Episode 73: Enumerations
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- Derick Rethans 0:14
Hi I'm Derick and welcome to PHP internals news that podcast dedicated to explain the latest developments in the PHP language.
- Derick Rethans 0:22
This is Episode 73. Today I'm talking with Larry Garfield, who you might recognize from hits such as object ergonomics and short functions. Larry has worked together with Ilija Tovilo on an RFC titled enumerations, and I hope that Larry will explain to me what this is all about. Larry, would you please introduce yourself?
- Larry Garfield 0:43
Hello World, I'm Larry Garfield, I am director of developer experience at platform.sh. We're a continuous deployment cloud hosting company. I've been in and around PHP for 20, some odd years now. And mostly as an annoying gadfly and pedant.
- Derick Rethans 1:00
Well you say that but in the last few years you've been working together with other people on several RFCs right, so you're not really sitting as a fly on the wall any more, you're being actively participating now, which is why I end up talking to you now which is quite good isn't it.
- Larry Garfield 1:15
I'm not sure if the causal relationship is in that direction.
- Derick Rethans 1:18
In any case we are talking about enumerations or enums today. What are enumerations or enums?
- Larry Garfield 1:26
Enumerations or enums are a feature of a lot of programming languages, what they look like varies a lot depending on the language, but the basic concept is creating a type that has a fixed finite set of possible values. The classic example is Boolean; a Boolean is a type that has two and only two possible values: true and false. Enumerations are way to let you define your own types like that to say this type has two values, sort ascending or descending. This type has four values, for the four different card suits in a standard card deck, or a user can be in one of four states: pending, approved, cancelled, or active. And so those are the four possible values that this variable type can have. And what that looks like varies widely depending on the language. In a language like C or c++, it's just a thin layer on top of integer constants, which means they get compiled away to integers at compile time and they don't actually do all that much, they're a little bit to help for reading. At the other end of the spectrum, you have languages like rust or Swift, where enumerations are a robust Advanced Data Type, and data construct of their own. That also supports algebraic data types, we'll get into that a bit more later. And is a core part of how a lot of the system actually works in practice, and a lot of other languages are somewhere in the middle. Our goal with this RFC, is to give PHP more towards the advanced end of enumerations, because there are perfectly good use cases for it so let's not cheap out on it.
- Derick Rethans 3:14
What is the syntax?
- Larry Garfield 3:15
Syntax we're proposing is tied into the fact that enumerations as we're implementing them, are a layer on top of objects, they are internally objects with some limitations on them
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